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Slope Stabilization

Customer has 100 x 25 foot bank that is about 1.5 x 1 slope they would like to dress up, get rid of the weeds and plant ground cover. They don't have the dough for walls and terracing.

One of my thoughts is to use geogrid, cover it with topsoil and then plant individual, ornamental shrubs. I am opposed to planting ground cover plants, e.g Ivy, because of their invasive nature.

Would geotextile work as well or better than geogrid. It seems that if I put four inches of topsoil on top of either the geogrid or geotextile that the topsoil will just wash away.The only way I can think to use GT or GD is to put down topsoil, put GT or GD on top, plant through it and cover the area with mulch. There will probably be some annual maintenance to reposition the mulch but the customer is OK with that.

The only way I have stabilized a slope this steep is with cobblestones or small rip rap, chinking and mortar. That won't look too good in a residential neighborhood. Can anyone think of any other options and is the use of GD or GT appropriate here?

Tom I just had a similiar project last week at a hospital. I fixed it..... I hope... by regrading the hillside to clean up the ruts and then installing geo-fabric, Mirafi, I dont remember which type, I then topped the fabric with 3" of topsoil and finally an erosion control blanket, ya know those ones made of coconut fibers and stapled it to the slope and we hydroseeded everything. I dont see why you couldnt plant a ground cover as opposed to the hydroseeding, but the most important thing we did that you will want to look into is redirecting the flow of water over the slope, is a riprapped swale out of the picture to direct and diffuse the water flow from the slope?

Comment

Thanks for the info. Here I am again looking at the problem and not the cause. You hit it. I can swale the top of the bank into a pipe and daylight the pipe into the road culvert that is about 30 feet away. That way the only water on the slope will be what has fallen there, none of the drainage from above will get to the slope.

Comment

I have had very good luck with pyramat in the past. Once the mat is secured to the slope a layer of topsoil can be overlayed and with the 3 dimensional nature of the mat the soil will remain in place and can then be seeded with the roots of the grass growing through the soil and the fabric. The only draw back to the mat is the fact that it is a little pricier than a traditional geotextile....

Comment

Soil is stable unless it is wet so the trick is to minimize the amount of irrigation and put in plants (trees) that will suck out the water. The neat thing about a tree is that its roots will seek out the areas where there is the most ground water percolating through the soil and suck it out. Far more effective than a man-made drainage system and can be done at a fraction of the cost.

Any ground cover should be drought tolerant and not need watering to grow or you really just create a bigger problem.

All you have to do is look at slopes in the area that are stable and others that have slumped or worse and you can see the difference the right vegetation makes and the problems caused up-slope from adding water to the mix.

Soil type makes a big difference and that includes more than just the surface topsoil. In California there is a lot of sandstone once you go done a foot along the coast and in Texas there is a hard pan and both make it slow going for many types of trees, especially non-native ones.